The present invention relates to a method for producing a novel thermoplastic elastomer composition which is flexible and tough in a wide range of temperature and is excellent in balance of properties such as mechanical properties and thermal properties and in appearance and can be used for automobile bumpers, sound deadening gears, sports shoes soles, tubes, hoses, and the like.
Hitherto, flexible vinyl chloride resins, ethylene-vinyl acetate resins, thermoplastic urethane resins, nylon 12, polyester elastomers and the like have been generally used as materials which provide hard rubbers or leather-like molded articles. However, flexible vinyl chloride resins have a problem in cold resistance, ethylene-vinyl acetate resins in wear resistance, thermoplastic urethane resins in processability, nylon 12 in cold resistance and polyester elastomers in hydrolysis resistance and thermal aging resistance and these must be improved.
Japanese Patent Kokai No. 61-40355 discloses a method for improving hydrolysis resistance and thermal aging resistance of polyester elastomers by blending block copolymer type polyester elastomers with carboxyl group and/or epoxy group-containing olefin polymers. However, this composition is poor in balance of properties such as stiffness, heat resistance, impact resistance, oil resistance and electric characteristics because the polyester component is block copolymer type elastomers.
Furthermore, Japanese Patent Kokai No. 55-137154 proposes to blend polyalkylene terephthalates, ethyleneglycidyl methacrylate copolymers and a polyfunctional compound selected from epoxy compounds, isocyanate compounds and carboxylic acid anhydrides.
Moreover, Japanese Patent Kokai No. 61-221260 teaches to blend thermoplastic polyesters with maleic anhydride grafted ethylene-propylene random copolymers and ethylene-glycidyl methacrylate copolymers. However, the above compositions are not satisfactory yet in balance of stiffness, heat resistance, impact resistance and oil resistance as elastomers because the blending materials, blending ratio and blending method are not proper.
Further, Japanese Patent Kokai No. 63-113056 discloses that a composition improved in compatibility, excellent in impact resistance at low temperature and good in balance with stiffness can be obtained by melt kneading a saturated polyester resin with a copolymer of an unsaturated epoxy compound and ethylene. The composition is considerably improved in these respects, but a further improvement in balance of low-temperature impact resistance, heat resistance, oil resistance and stiffness is required for industrial use thereof.